It isn't just an "rpm" sensor.

Your '92 engine's computer has the responsibility, formerly the responsibility of the distributor's Hall effect sensor in older model year cars (and points in still much older distributors), of determining the proper instant (in relation to crankshaft position) to trigger the spark. Your distributor no longer has all the weights and springs (and vacuum diaphragm) found in older model years -- it (functionally speaking) only has the rotor to divert the spark to the proper spark plug, but the exact timing of the spark (based on rpm, load, etc.) is now a software algorhythm, and it is essential that the computer know exactly where the crankshaft is in its rotation. It does this with signals from the CPS (Crankshaft Position Sensor) that sits over the tone ring.

Without the tone ring, the computer will not have that information, and the engine will not run.